What defines a mini-split A/C system that heats in winter and cools in summer?

A mini-split A/C system that is capable of heating in winter and cooling in summer is defined as a heat pump. Heat pumps operate by transferring heat rather than generating it, which allows them to provide both heating and cooling functionality. In cooling mode, a heat pump extracts heat from the indoor space and releases it outside, similar to a standard air conditioner. Conversely, in heating mode, the process is reversed: the heat pump collects heat from outside—even in cold weather—and transfers it indoors.

The term "heat pump" specifically refers to this dual functionality and emphasizes the equipment's ability to move heat in both directions, making it an ideal solution for climate control year-round. This adaptability is particularly beneficial in areas with moderate climates, where a heat pump can efficiently maintain comfortable indoor temperatures throughout the year.

While a reversible air conditioner also refers to a system that can switch between heating and cooling, the more technical and broader term that encompasses all aspects of this operation is "heat pump." Options relating to a dual compressor system or a heat exchanger do not specifically describe the dual functionality of heating and cooling.